Degradation of Membrane Phosphoglycerides by the Reversal of Phosphotransferase Reactions
Phosphocholine and phosphoethanolamine transferases of different tissues catalyze reversible reactions. The role of the “direct reactions” is well established because they lead to the biosynthesis of choline and ethanol-amine phosphoglycerides (CPG and EPG) from diglycerides and CDPamines. Whether or not “back-reactions” might have metabolic importance is still under discussion. In the past, we have reported that diglycerides, produced from brain microsomal phospholipids by the reversal of phosphotransferase reactions, become available for diglyceride lipase and free fatty acids (FFA) are released (1,2). Thus, we have postulated a CMP-dependent pathway for the degradation of microsomal CPG and EPG. Further studies have indicated that this mechanism might contribute to the release of FFA during an energy deficiency such as brain ischemia (3). Alternatively, diglycerides produced by the “back-reaction” could be utilized for the synthesis of other phospholipid molecules (interconversion). The rate of the formation of diglycerides and their fate depend on the relative concentration of CMP, CDPcholine, and CDPethanolamine (4). Both aspects are summarized in Fig. 1.
KeywordsFree Fatty Acid Platelet Lysate Platelet Suspension Human Platelet Lysate Choline Phosphoglycerides
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